William Sloane Coffin Jr., 81, a Presbyterian clergyman and former Yale University chaplain whose early activism against the Vietnam War brought him international notoriety during a lifelong career of civil disobedience, died April 12 at his home in Strafford, Vt. He had congestive heart failure.

From the moment in 1958 when Mr. Coffin roared onto Yale’s campus atop his motorcycle, he signaled that his presence would mean a distinctly radical approach to the social, political and moral upheaval that defined the next decade.

Mr. Coffin called himself a “Christian revolutionary” and believed that his outspoken activism sprang from the principles of his faith.

His 18-year tenure at Yale encompassed the civil rights struggle and the Vietnam War, each of which he confronted in bold and daring fashion.